For the most part, just the fact that "Harmonic Tremors" is released on Hydra Head should give you at least an inkling that it is an album that contains flourishes of ISIS' patented ethereal-tinged and earth moving approach. That the project was named for the 50-foot effigy burned annually at the Fiestas De Santa Fe in Santa Fe, New Mexico and is the project of CAVE IN/OLD MAN GLOOM bassist Caleb Scofield (with assistance on drums from OLD MAN GLOOM's Santos Montano) should seal the deal. "Harmonic Tremors" is a doom album at its core, although the CAVE IN atmospherics and trippy dirges of some of Hydra Head's better known bands make it a far more abstract and simmering affair.
More than anything else, "Harmonic Tremors" is defined by its growling bass tone, more like a menacing serpent than an instrument with four strings. It is that bottom end rumble and the sleepy melodies that converge with Scofield's gruff and groaning vocals, mixed with semi-spacey clean vocals, that makes the album sound like an unidentifiable organic mass that roves across the room as the album plays. The opening track, "The Blessing", contains the album's most tuneful and upbeat (well, kind of) melody and dreamy aura, though not without plenty of beefy reverberations. Much of the rest involves the alternating clean and gnarly vocals, lava flowing tempos, and otherworldly vibes. But it keeps coming back to those impossibly thick bass lines, often driving tough movers like "Invisible Wolves".
In the end it is all about the rumble and the tripped nature of the beast, weather wafting vocals or churning riffs. "Harmonic Tremors" does indeed make you feel as though the earth is moving beneath your feet as the head leaves the body for a sojourn to the other side.